Synchronous frequency broadcasting



Jan. 4, 1949.

Filed Nov. 14, 1944 R. M; WILMOTTE SYNCHRONOUS FREQUENCY BROADCASTING- 2Shee'ts-Shet 1 P ayi a 4 f f I I I SIGNAL POWER SOURCE AMPLIFER .2 7 e-I I I 5.0. FREQ. MODULAT- UHF.

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Patented Jan. 4, 1949 SYNCHRONOUS FREQUENCY BROADCASTING Raymond M.Wilmette, Washington, D. 0. Application November 14, 1944, Serial No.563,391

11 Claims.

This invention relates to synchronous frequency broadcasting and theoperation of booster or satellite stations in conjunction with a primarybroadcast station.

In operating a booster or satellite station, it is important to avoidvariable relative phase shifts between the video or audio signals andbetween the carrier waves transmitted by the primary station and thebooster stations, otherwise interference will result in zones served bymore than one of these stations.

It is an, object of this invention to provide a broadcasting systemwhich will not give rise to interference and will insure synchronizedbroadcasting at the primary and booster stations.

The invention will be more fully understood from the followingdescription and the attached drawing in which:

Figure 1 is a schematic diagram of primary broadcast station.

Figure 2 is a schematic diagram of a booster station.

Figure 3 is a schematic diagram of multiple program primary station,

Figure 4 shows a combined booster and relay station, and

Figure 5 illustrates the relative arrangement of a primary broadcastingstation and a plurality of satellite stations, as well as the relationsof the radiation patterns produced thereby.

Figure 1 shows a modulator 3 which modulates radio frequencyoscillations derived from the broadcast frequency source 2 with signalsfrom a source I. The output of the modulator may be amplified in thepower amplifier 4 and broadcast by an antenna 5. A source of ultra highfrequency oscillations 6 and the modulator 3 are connected to amodulator I. The ultra high frequency oscillations may be of the orderof 1000 megacycles or any other suitable frequency oscillations. Themodulated ultra high frequency oscillations at the output of themodulator 1 may be amplified in amplifier 8 and transmitted by anantenna 9. The antenna 9 may be a highly directive radiator, asindicated in the drawing.

The energy from the antenna 3 is picked up by an antenna l anddemodulated by a detector |2 after passing through amplifier H. Theamplifier H is optional and may be omitted if extremely high frequenciesare used. The output of detector I2 is a replica of the modulated radiofrequency waves broadcast by the antenna of the primary station. Theradio frequency oscillations from detector |2 are amplified in amplifierl3 and broadcast by antenna M. In this 2 manner the same modulated radiofrequency waves are broadcast in both the primary and the boosterstations.

Figure 3 shows a primary station similar to 5 Figure 1 except that aplurality of radio frequency oscillators 22, 3|, each feed a modulator23 or 33 connected to signal sources 2| and 32. In practice, one signalsource may be a television source and the other may be an audio siglOnal source. The oscillator 22 may generate oscillations of a frequencybetween 500 and 1500 kilocycles and oscillator 3| may generate afrequency of the order of 50 megacycles for television or FMbroadcasting. The outputs of the modulators 23 and 33 are fed tobroadcasting antennas 25 and 35 through power amplifiers 24 and 34. Theoutputs of these modulators are also fed to a modulator 21 to modulateultra high frequency oscillations derived from the oscillator 26. Theoutput of modulator 21 is radiated by a directive antenna 28.

At the booster station, shown in Figure 4, the ultra high frequencywaves are picked up by an antenna 4| and demodulated by a detector 42.An amplifier, not shown, may be connected ahead of the detector, ifdesired. A filter 43 selects one of the modulated carrier wavesappearing at the output of the detector 42 and this carrier wave isamplified in amplifier 44 and radiated by antenna 45. A second filter 46selects one or more of the modulated carrier waves at the output of thedetector 42. A modulator 48 is connected to the filter 46 and to ultrahigh frequency oscillator 41 for modulating the ultra high frequencywith the modulated carrier waves passed by the filter 46. The frequencyof the oscillations of oscillator 41 is preferably difierent from thefrequency of the waves received by antenna 4|. The output of themodulator 48 is radiated by the antenna 49. The energy radiated byantenna 43 may be picked up by another station similar to the one shownin Figure 4 or by a booster station such as shown in Figure 2. Aplurality of booster stations of either the type shown in Figure 2 orFigure 4 can be operated in conjunction with the primary stations ofFigure 1 or 3. Instead of demodulating the incoming signal and supplyinganother carrier from oscillator 41, the waves received by antenna 4| 50may be amplified and directly fed to antenna 49. Other modificationswithin the scope of this invention as defined by the following claimswill be apparent to those skilled in this art.

Reference is now made of Figure 5 of the drawings wherein is illustrateda single broadcasting station operating in conjunction with a pair ofbooster or satellite stations. Reference numeral 50 denotes a primarystation of the type illustrated in detail in Figure 3 of the drawings,and which has been described in detail in the preceding portions of thespecification, and includes one or more substantially omni-directionallytransmitting antennae 25, 35 for transmitting primary broadcasts into anarea generally denoted by the reference numeral The primary station 50further provides means for transmitting an ultra high frequency carriervia an antenna 28, this ultra high frequency carrier being modulatedwith the signals transmitted by the antennae 25 and 35, and the antenna28 being in general directional, and transmitting signals to the boosterstations 52 and 53, each of which includes a directional receivingantenna 4| for receiving the ultra high frequency transmissions.

Booster stations 52 and 53 may be of the character illustrated in Figure4 of the drawings, the latter figure including as a special case asystem of the character illustrated in Figure 2 of the drawings.Accordingly, the booster stations 52 and 53 are provided with theprogram transmitted by the primary station 50, modulated, however, on anultra high frequency carrier. Booster stations 52 and 53 are providedwith detecting means for abstracting from the ultra high frequencycarrier the modulated low frequency or broadcasting carrier impressedthereon, and for re-transmitting the latter omni-directionally viaantennae 45 at each of the booster stations.

In the normal operation of a satellite system or synchronous frequen ybroadcasting system of the character herein involved, the boosterstations 52 and 53 are in relatively close proximity to the primarystation 50, and are arranged to provide radiation patterns 54 and 55,respectively, which overlap the radiation pattern 51 provided by theprimary station 50 and which, furthermore, mutually overlap to assist inobtaining broadcast coverage over an area.

Accordingly, the primary station 50, when taken in conjunction with thebooster stations 54 and 55, is capable of serving a much greater areathan is the primary station 50 by itself, and in the case of relativelyhigh frequency signals such as those utilized in transm'tting televisionprograms, the efiects of intervening geographic obstacles and the likemay be overcome,

It will be realized that while I have illustrated in Figure 5 of thedrawings a system utilizing two booster stations, that in practice anynumber of such stations may be utilized within the scope of theinvention, and in accordance with the necessities of given situations.For example, where extremely hilly country must be covered inbroadcasting television programs, or where a very extended area must becovered it may be desirable to provide a greater number of boosterstations than two.

While I have described various embodiments and arrangements inaccordance with my invention, it will be realized that modificationsthereof may be resorted to without departing from the true spirit andscope of the invention.

I claim:

1. A synchronous frequency broadcasting system including a primary radiobroadcasting station having a source of signals, a source of radiofrequency oscillations, a modulator for modulating said radio frequencyoscillations in response to said signals to provide modulated radiofrequency energy, means for radiating said modulated radio frequencyenergy, a source of further radio frequency oscillations, meansresponsive to said modulated radio frequency energy for modulating saidfurther radio frequency oscillations with said modulated radio frequencyenergy to provide doubly modulated radio frequency oscillations, andmeans for radiating said doubly modulated radio frequency oscillations.

2. A synchronous frequency broadcasting system including a primarybroadcasting station having a signal source, a source of radio frequencyoscillations, a modulator connected to said sources, an antennaconnected to said modulator for radiating modulated radio frequencyoscillations derived from said modulator, a source of oscillations of amuch higher frequency than said radio frequency oscillations, means formodulating said higher frequency oscillations with said modulated radiofrequency oscillations and means for transmitting said higher frequencyoscillations.

3. A system in accordance with claim 2 wherein is further provided asatellite station having means for receiving said higher frequencyoscillations, means for demodulating said higher frequency oscillationsto obtain said modulated radio frequency oscillations, and means forradiating said modulated radio frequency oscillations.

4. A synchronous frequency broadcasting system including a primarybroadcasting station having means for generating a plurality ofmodulated radio frequency carrier waves having nonoverlapping sidebands,a generator of ultra high frequency oscillations, means for modulatingsaid ultra high frequency oscillations with said modulated carrierwaves, an antenna for radiating one of said carrier waves and an antennafor radiating said ultra high frequency oscillations modulated with saidmodulated carrier waves.

5. A system in accordance with claim 4 wherein is further provided asatellite station having an ultra high frequency receiving antenna, adetector for demodulating said ultra high frequency oscillations toderive said radio frequency carrier waves, and means for selectivelyradiating at least one of said carrier waves.

6. A system in accordance with claim 2 wherein is further provided a.relay station having means for receiving said higher frequencyoscillations and for demodulating said higher frequency oscillations toobtain said modulated radio frequency oscillations, a source ofoscillations of much higher frequency than said radio frequency andmeans for modulating said last mentioned higher frequency oscillationswith said modulated radio frequency oscillations to provide doublymodulated higher frequency oscillations, and means for radiating saiddoubly modulated higher frequency oscillations,

7. A system in accordance with claim 4 wherein is further provided asatellite station having an ultra high frequency receiving antenna, adetector for demodulating said ultra high frequency oscillations toderive said carrier waves, means for selectively radiating at least oneof said carrier waves, an ultra high frequency oscillator, means formodulating the ultra high frequency output of said oscillator with atleast one of said carrier waves and an antenna connected to the lastmeans for radiating the modulated ultra high frequency output of saidlast means.

8. A synchronous frequency broadcasting system including a primarybroadcasting station having a signal source, a source of radio frequencyoscillations, a modulator connected to said sources, an antennaconnected to said modulator for radiating, substantiallyomni-directionally, modulated radio frequency oscillations derived fromsaid modulator, a source of oscillations of a much higher frequency thansaid radio frequency oscillations, means for modulating said higherfrequency oscillations with said modulated radio frequency oscillations,means for transmitting said higher frequency oscillations, a pluralityof satellite stations each having means for receiving said higherfrequency oscillations and means for demodulating said higher frequencyoscillations to obtain said modulated radio frequency oscillations, saidplurality of satellite stations having means for substantiallyomni-directionally broadcasting said modulated radio frequencyoscillations in mutually overlapping radiation patterns.

9. A synchronous frequency broadcasting system including a primarybroadcasting station having means for generating a plurality ofmodulated radio frequency carrier waves having nonoverlapping sidebands, a generator of ultra high frequency oscillations, means formodulating said ultra high frequency oscillations with said modulatedcarrier waves, an antenna for radiating one of said carrier waves in apredetermined radiation pattern, and an antenna for radiating said ultrahigh frequency oscillations modulated with said modulated carrier waves,a plurality of satellite stations having each an ultra high frequencyreceiving antenna for receiving ultra high frequency oscillations and adetector for demodulating said ultra high frequency oscillations toderive therefrom said radio frequency carrier waves, and'means forselectively and substantlally omni-directionally radiating at least oneof said carrier waves from each of said plurality of satellite stationsin radiation patterns overlapping said predetermined radiation pattern.

10. A synchronous frequency broadcasting system including a primarybroadcasting station having a signal source, a source of radio frequencyoscillations, a modulator connected to said sources, an antennaconnected to said modulator for radiating, substantially omni-direction-I ally, modulated radio frequency oscillations derived from saidmodulator, a source of oscillations of a much higher frequency than saidradio frequency oscillations, means for modulating said higher-frequencyoscillations with said modulated radio frequency oscillations, means fortransmitting said higher frequency oscillations, a relay station havingmeans for receiving said higher frequency oscillations and fordemodulating said higher frequency oscillations to obtain therefrom saidmodulated radio frequency oscillations, a source of oscillations of muchhigher frequency than said radio frequency, means for modulating saidlast mentioned higher frequency oscillations with said modulated radiofrequency oscillations to provide doubly modulated higher frequencyoscillations, means for radiating said doubly modulated higher frequencyoscillations, and means for radiating said last mentioned modulatedradio frequency oscillations.

1 A synchronous frequency broadcasting system including a primarybroadcasting station having means for generating a plurality ofmodulated radio frequency carrier waves having nonoverlapping sidehands, a generator of ultra high frequency oscillations, means formodulatin said ultra high frequency oscillations with said modulatedcarrier waves, an antenna for radiating one of said carrier waves and anantenna for radiating said ultra high frequency oscillations modulatedwith said modulated carrier waves, a plurality of satellite stationshaving each an ultra high frequency receiving antenna and a detector fordemodulating said ultra high frequency oscillations to derive saidcarrier waves and means for selectively and substantiallyomni-directionally radiating at least one of said -last mentionedcarrier waves, an ultra high freand an antenna connected to said lastnamed means for radiating the modulated ultra high frequency output ofsaid last named means.

RAYMOND M. WIIMO'ITE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,397,093 Espenschied Nov. 15,1921 1,403,841 Carson Jan. 1'7, 1922 1,447,204 Espenschied Mar. 6, 19231,799,978 Falknor Apr. 7, 1931 1,858,349 Terman May 17, 1932 1,987,616Gebhard Jan. 15, 1985 2,017,128 Kroger Oct. 15, 1935 2,028,212 HeisingJan. 21, 1936 2,155,821 Goldsmith Apr. 25, 1939 2,175,270 Koch Oct. 10,1939 2,257,917 Pungs Oct. 7, 1941 2,284,415 Goldstine May 26, 19422,304,969 Trevor Dec. 15, 1942 2,344,813 Goldstine Mar. 21, 1944 FOREIGNPATENTS Number Country Date 481,841 Great Britain Mar. 18, 1938 409,115Great Britain Apr. 26, 1934

